Plate-and-fin heat exchanger fins with bending points
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Solution Overview
Problem
Current plate-and-fin heat exchangers experience cracks in braze joints due to high thermal transients, leading to a need for a more robust interface between the plate and fins.
Innovation Solution
The core assembly features fins with bending points that create multiple points of contact with core plates, secured by a braze joint with a finer crystalline microstructure, using alloys like aluminum silicon, stainless steel, and copper-based alloys, and a thickness of less than 100 micrometers, enhancing mechanical and thermal properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional fins without bending points are used, then the structure is simpler and easier to manufacture, but the braze joints develop cracks under high thermal transients
Solution Approach 1:
The fin is designed with a bending point that creates a curved profile instead of a straight configuration. This curvature allows the fin to accommodate thermal expansion and contraction by flexing at the bending point, thereby preventing crack formation in the braze joints while maintaining structural integrity under high thermal transients.
Solution Approach 2:
The fin structure is modified by introducing a bending point that changes the geometric parameters of the fin. This parameter change enables the fin to deform elastically under thermal stress, converting the rigid structure into a flexible one that can absorb thermal cycling without causing braze joint failure.
2Reliability
If multiple bending points are added to fins, then thermal fatigue resistance improves, but manufacturing complexity increases
Solution Approach 1:
Multiple bending points are introduced along the fin length, each creating a curved section. These curved sections act as flexible joints that distribute thermal stress along the fin, significantly improving thermal fatigue resistance. The consistent curved profile can be achieved through standardized manufacturing processes.
3Temperature
If braze joint thickness is reduced below 100 micrometers, then thermal conductivity improves, but joint strength may be compromised
Solution Approach 1:
The braze joint thickness parameter is optimized to be less than 100 micrometers. This parameter change enhances thermal conductivity by reducing the thermal resistance of the joint. The fin's bending capability compensates for the reduced joint thickness by providing mechanical flexibility that prevents stress concentration at the joint interface.
Solution Approach 2:
The braze joint is formed using specialized alloys that combine high strength with good thermal conductivity. The composite structure of the braze material, combined with the flexible fin design, allows for thin joints that maintain both mechanical strength and thermal performance under thermal cycling conditions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design improves thermal fatigue and mechanical strength, reducing the likelihood of cracks and enhancing durability, thus addressing the issue of thermal expansion and contraction.
Implementation Method 1
Each bending point create two points of contact between a core plate and the heat-absorbing member... improves thermal fatigue and mechanical strength, reducing the likelihood of cracks
Implementation Method 2
The heat-absorbing member is secured to the pair of core plates by a braze joint... a thickness of the braze joint is measured from a crest of the one or more bending points and a surface of a respective core plate
Data Source
AI summary
A core assembly for a plate-and-fin heat exchanger includes a pair of core plates and a heat-absorbing member disposed within the passageway that secures the pair of core plates together. The heat-absorbing member defines a plurality of fins that each include one or more bending points, and each bending point creates two points of contact between a core plate and the heat-absorbing member.